LAUSR

Satellite cells (SC) and ribosomes are key determinants of the skeletal muscle adaptive response. Both are thought to increase acutely after resistance exercise and chronically with resistance training. However, the acute SC and ribosome exercise response with prior aerobic conditioning is unknown. Fourteen young men and women underwent 6 weeks of single-legged aerobic conditioning followed by an acute bout of 300 eccentric contractions. Muscle biopsies were taken from the vastus lateralis of the aerobically conditioned (AC) and the control (CTL) legs before (Pre), 24 (24h) and 48 (48h) hours post-contractions. SC pool expansion (PAX7+ cells/100 fibres) was greater in type-I (1.3-fold) and mixed-fibres (1.2-fold) in the AC leg compared to the CTL. Pax7 (1.2-fold) and MyoD1 (1.4-fold) mRNA expression was also greater in the AC leg compared to the CTL. AC had greater RNA concentration (1.2-fold) and mRNA expression of Ubf (1.2-fold) and Tif-1a (1.3-fold) compared to CTL. Only the AC leg increased (Pre-48h) c-Myc (3.0-fold), (Pre-24h) 45S pre-rRNA (2.6-fold), 5.8S ITS (2.1-fold) and 28S ITS (2.0-fold) following eccentric contractions. We discovered that aerobic conditioning augmented type-I SC pool expansion and ribosome content following an acute bout of eccentric contractions.